Seriously? Google it, I'm sick and tired of these lazy questions. It's even been answered on Tom's like 100 times and probably 100 times on google. The time you took you type out the question, you could have already known.
i'm with getochkn here, i mean it's ok to not know something, even if it's something basic as this, but guys, we're on the internet here, we have search engines. so please just type your question into google and be astonished how fast you got your answer, without spamming some tech-forum for the millionth time with the same simple question. no offense meant, it's just a thing of priciple.